[Mine] ESP32 -> AWS IoT -> DynamoDB via MQTT

esp32awsiot.ino

#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <PubSubClient.h>

#define LED_PIN 2
#define BUTTON_PIN 0

/* Change the following configuration options */
const char* ssid = "";
const char* password = "";
const char* aws_iot_hostname = "";
const char* aws_iot_sub_topic = "";
const char* aws_iot_pub_topic = "";
const char* aws_iot_pub_message = "{\"led_state\": %d}";
const char* client_id = "MyIoT";

const char* ca_certificate = ""; //CA certificate
const char* iot_certificate = ""; //Own certificate
const char* iot_privatekey = ""; //Own private key

#define SSID_HAS_PASSWORD //comment this line if your SSID does not have a password

/* Global Variables */
WiFiClientSecure client;
PubSubClient mqtt(client);
bool released = true;
bool led_state = LOW;
char buffer[50];

/* Functions */
void sub_callback(const char* topic, byte* payload, unsigned int length) {
  Serial.print("Topic: ");
  Serial.println(topic);

  Serial.print("Message: ");
  for (int i = 0; i < length; i++)
    Serial.print((char) payload[i]);
  Serial.println();

  if ((char) payload[0] == '1')
		led_state = HIGH;
  else if ((char) payload[0] == '0')
		led_state = LOW;
	
	digitalWrite(LED_PIN, led_state);
}

void setup() {
  //Initializations
  Serial.begin(9600);
  Serial.print("Attempting WiFi connection on SSID: ");
  Serial.print(ssid);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);
	pinMode(BUTTON_PIN, INPUT);

  // WiFi
  #ifdef SSID_HAS_PASSWORD
  WiFi.begin(ssid, password);
  #else
  WiFi.begin(ssid);
  #endif

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print('.');
  }
  Serial.print("\nWiFi connection succeeded.\n");

  client.setCACert(ca_certificate);
  client.setCertificate(iot_certificate);
  client.setPrivateKey(iot_privatekey);

  // AWS IoT MQTT uses port 8883
  mqtt.setServer(aws_iot_hostname, 8883);
  mqtt.setCallback(sub_callback);
}

void loop() {
  // reconnect on disconnect
  while (!mqtt.connected()) {
    Serial.print("Now connecting to AWS IoT: ");
    if (mqtt.connect(client_id)) {
      Serial.println("connected!");
      mqtt.subscribe(aws_iot_sub_topic); //subscribe to the topic
    } else {
      Serial.print("failed with status code ");
      Serial.print(mqtt.state());
      Serial.println(" trying again in 5 seconds...");
      delay(5000);
    }
  }

	// check if button is pressed
	if (digitalRead(BUTTON_PIN) == LOW && released) {
		released = false;

		sprintf(buffer, aws_iot_pub_message, led_state);
		Serial.println("Button is pressed. Publishing MQTT message...");
    mqtt.publish(aws_iot_pub_topic, buffer);
	}

	if (!released)
		released = digitalRead(BUTTON_PIN);

  mqtt.loop();
}